Stabilized propellant compositions and methods for their preparation

ABSTRACT

CERTAIN ORGANIC COMPOUNDS, CALLED STABLIZERS, HAVE BEEN DISCLOSED AS BEING USEFUL INPREPARING SOLID PROPELLANTS HAVING HYDRAZINIUM DIPERCHLORATE (HP2) AS AN OXIDIZER. BY USE OF THESE STABILIZERS, THE USEFUL HYDROCARBON POLYMER FUEL BINDER, E,G., POLYALKADIENE FUEL BINDER, ARE RENDERED COMPATIBLE WITH HP2 WHERE PREVIOUSLY HP2 AND THE BINDER REACTED RESULTING IN A HARD BRITTLE MASS UNSUITABLE AS A PROPELLANT. THE STABILIZING COMPOSITIONS OF THE INVENTION USUALLY ARE SULFUR AND NITROGEN CONTAINING COMPOUNDS WHEREIN THE SULFUR AND NITROGEN ARE USUALLY BOUND IN A HETEROCYCLIC RING AND HAVE (A) WEAKLY BASIC CHARACTERISTICS AND/OR (B) ALIPHATIC SUBSTITUENTS AND/OR (C) HETEROCYCLIC SUBSTITUENTS.

United States Patent Int. Cl. C0611 /06 U.S. Cl. 149-19 34 Claims ABSTRACT OF THE DISCLOSURE Certain organic compounds, called stabilizers, have been disclosed as being useful in preparing solid propellants having hydrazinium diperchlorate (HP as an oxidizer. By use of these stabilizers, the usual hydrocarbon polymer fuel binder, e.g., polyalkadiene fuel binder, are rendered compatible with H1 where previously HP; and the binder reacted resulting in a hard brittle mass unsuitable as a propellant. The stabilizing compositions of the invention usually are sulfur and nitrogen containing compounds wherein the sulfur and nitrogen are usually bound in a heterocyclic ring and have (a) weakly basic characteristics and/or (b) aliphatic substituents and/or (0) heterocyclic substituents.

This invention relates to a process for improving the curability of certain solid propellant compositions containing hydrazinium diperchlorate oxidizer and hydrocarbon binders, as well as the propellant compositions resulting from this process.

More particularly, this invention concerns certain stabilizing compositions which, when added to hydrazinium perchlorate based propellant compositions prior to curing, prevent premature curing and overcuring of the propellant mixture. The propellant compositions of this invention can be cured to a propellant having superior physical and aging properties.

Hydrazinium diperchlorate (HP is an exceedingly energetic oxidizer. In addition to its exceptional potency, it has certain other advantages which would make it a desirable oxidizer component in solid propellant compositions. These advantages include high density, a high burning rate and relatively low sensitivity toward detonation from shock. In addition, the HP is available in large quantities in a high state of purity at relatively moderate cost. The high density of the H1 permits high loading levels compared to many less energetic oxidizers. This in turn increases the available energy of the propellant composition on a unit weight basis and increases the potential range of the rocket hardware. The relatively low shock sensitivity of HP facilitates formulating, handling and storage while availability and purity permit long term planning. All of these attributes of HP are important considerations in military and aerospace operations.

Unfortunately, HP has several defects which have prevented its widespread use in conjunction with many high energy binders such as the energetic hydrocarbon binders. Among these defects are poor compatibility, a short processing life and, most important, poor curing properties when compounded with most of the desirable hydrocarbon fuel binders of the art.

Compatibility is an especially acute problem when HP is formulated which polyalkadiene fuel binders containing 3,741,830 Patented June 26, 1973 ice reaction sites other than the unsaturated carbon to carbon bonds. These reaction sites are incorporated into the binder to facilitate curing of the binders. These sites include, among many others, carboxyl, carbonyl, epoxy, amino and the lie. For reasons presently unknown, polyalkadienes containing these groups rapidly react with HP to form an overcured (excessively crosslinked) hard and brittle material unsuitable for propellant use. The unusual thing is that this pseudo curing takes place even in the complete absence of curing agents. Until the present time, all previous attempts to obviate or to reduce the premature curing of HP -polyalkadiene propellant compositions have been unsuccessful.

That premature curing is a problem in HP -hydrocarbon compositions at all is most surprising in that the less energetic but presumably chemically equivalent perchlorate, ammonium perchlorate, acts as an inert filler insofar as curing is concerned. That is, ammonium perchlorate and the other perchlorates commonly used as oxidizers in the solid propellant art do not cause curing in the propellant mix in the absence of curing agent. For example, When ammonium percholrate is formulated with a carboxyl terminated polybutadiene with the usual propellant adjuvants, the admixed propellant remains fluid and uncured until a curing agent is added to the mix and the temperature is raised to the curing temperature. Furthermore, when a prior art curing agent such as a trifunctional imine is blended into the propellant composition and the temperature is raised to a curing temperature, a flexible solid propellant having good aging and physical properties is produced.

In contrast, when HP is substituted on a weight by weight basis for ammonium perchlorate in the above composition, the composition cures within a few hours to an undesirably hard and brittle state even in the absence of the imine curing agent.

Because of their poor physical and aging characteristics, the use of HP -hydrocarbon propellants has been disparaged in the art. As a result of the inability to utilize the economical and commercially available hydrocarbon resins with HP oxidizer, a good deal of effort has gone into programs to develop satisfactory HP propellant compositions using a variety of binders. In spite of the development of many costly exotic binders and a great deal of time, no truly satisfactory HP based solid propellant compositions have been developed. That is, the resultant propellants give only fair cures and hence have relatively poor mechanical properties. In addition, such exotic binders are diflicult to cure and are expensive to prepare.

Thus, the development of inexpensive HP -hydrocarbon propellant not subject to premature curing and overcuring would be a notable advance in the art. Particularly desirable would be a stable inexpensive HP -hydrocarbon binder propellant composition combining good curing and aging properties.

It is therefore an object of this invention, among others, to develop a method of improving the curability and compatibility of HP -hydrocarbon propellant compositions.

It is a related object of this invention to prepare highly energetic propellant compositions not subject to premature overcuring to a brittle state.

Another more specific object of this invention is to stabilize HP -polybutadiene propellant compositions, said polyalkadiene resins can contain reactive sites such as epoxy, hydroxy, carboxy, amino groups in addition to their carbon to carbon unsaturation.

Yet another object of this invention is to prepare novel and highly energetic HP based propellant compositions containing hydrocarbon binder having good aging and physical properties both in the cured and uncured state.

Further objects are to prepare novel solid propellants having superior physical properties and pot life."

The above objects, among others, are achieved by incorporating a relatively small amount of a novel stabilizer into the propellant mixture prior to curing, preferably during the blending operation. The amount of stabilizer required to prepare a properly cured propellant having good physical and aging characteristics is hereinafter referred to as a stabilizing amount. This quantity cannot be stated precisely since it depends upon several variables including the quantity of HP in the propellant, the particular hydrocarbon binder used and the choice of stabilizer. In most instances, a stabilizing amount has been found to range between about 0.10 and 6.0 parts by weight or stabilizer for each 100 parts by weight of uncured compounded propellant. However, in some cases, greater and lesser amounts of stabilizer have been used successfully.

The formulated, stabilized solid propellant composition consists essentially of the following components in the indicated range of proportions.

(1) From about 0.10 to 6.0 parts by weight of the inventive stabilizer(s).

(2) From about 45 to 85 parts by weight of HP; (hydrazinium diperchlorate) including supplementary oxidizer(s).

(3) From about 10 to 40 parts by weight of a hydrocarbon binder including 0.5-10 parts by weight of ouring agent, curing catalysts and the like, and

(4) Up to about 25 parts by weight of optional propellant adjuvants, ordinarily from to 16 parts by weight of these optional components.

The above components of the propellant composition are blended, mixed or otherwise combined to yield a homogenous propellant mixture, then the mixture is cast into a rocket engine and cured at elevated temperature until the desired state of cure is obtained.

In practice, a stabilizing amount of stabilizer is blended with a hydrocarbon binder having reactive sites such as epoxy, hydroxy, amino and the like, curing agents, with any optional propellant adjuvants, such as surfactants, anticaking agents, coolants, burning rate catalysts, powdered high energy metals and the like, until a homogenous mixture is produced. At this time, the HP oxidizer is added with continuous blending. The blending (i.e., mixing) is continued until a homogenous and uniform uncured solid propellant is produced. The total blending time is dependent upon the batch size, the binder and stabilizer used, the viscosity of the formulation as well as other experimental variables, and thus cannot be stated with precision. However, in general, the mixing or blending time ranges between 30 minutes to 2 hours or more; although even somewhat longer mixing times are not harmful. After the propellant mixture has been blended, it is ordinarily cast into an engine casing and cured at temperatures ranging between about 100 F. and 200 F. until the required state of cure is obtained. The precise curing temperature and cure times are dependent upon variables such as the molecular weight of the binder, the nature and quantity of its reactive sites, whether these sites are terminal or secondary, the ratio of the components and the degree of hardness sought.

Because of these diverse considerations, the curing temperatures and times cannot be stated with precision. However, in propellant formulations containing 60-70 parts by weight of HP 15-20 parts by weight of carboxyl containing polybutadiene binder, 1-3 parts by weight of trifunctional imine curing agent and 15-20 parts by weight of propellant adjuvants, the following curing times and temperatures are representative:

Time in days: Curing temperature, F.

The following list of trifunctional imines are among the preferred curing agents for the propellant compositions of this invention:

tri(l-aziridinyl) phosphine oxide tri(2-methyl-l-aziridinyl) phosphine oxide tri(2,3-dimethyl-1-aziridinyl) phosphine oxide tri(2-isopropyl-l-aziridinyl) phosphine oxide tri(2-methyl-3-ethyl-l-aziridinyl) phosphine oxide tri(2-isopropyl-l-aziridinyl) phosphine oxide tri(2-methyl-3-n-butyl-l-aziridinyl) phosphine oxide tri(2-hexyl-1-aziridinyl) phosphine oxide tri(2,3-diheptyl-l-aziridinyl) phosphine oxide tri(2-methyl-3-octyl-l-aziridinyl) phosphine oxide tri(2-ethyl-3-decyl-l-aziridinyl) phosphine oxide tri(2-dodecyl-l-aziridinyl) phosphine oxide tri(2-methyl-3-tridecyl-l-aziridinyl) phosphine oxide tri(2-ethyl-3-octadecyl-l-aziridinyl) phosphine oxide tri(Z-eicosyl-l-aziridinyl) phosphine oxide tri(2-methyl-3-cyclopentyl-l-aziridinyl) phosphine oxide tri(2-ethyl-3-cyclohexyl-l-aziridinyl) phosphine oxide tri(2-n-butyl-3-(4-methylcyclohexyl)-1-aziridinyl) phosphine oxide tri(2-phenyl-l-aziridinyl) phosphine oxide tri(2-phenyl-3-tetradecyl-l-aziridinyl) phosphine oxide tri(2,3-diphenyl-l-aziridinyl) phosphine oxide tri(2-tert-butyl-3-phenyl-l-aziridinyl) phosphine oxide tri(2-ethyl-3-(l-napthyl) l-aziridinyl) phosphine oxide tri(2-n-propyl-3-(Z-naphthyl) l-aziridinyl) phosphine oxide tri(2-methyl-3-benzyl-l-aziridinyl) phosphine oxide tri(2-monyl-3-benzyl-1-aziridinyl) phosphine oxide tri(2-n-propyl-3-(2-phenylethyl) l-aziridinyl) phosphine oxide tri(2-methyl-3- (4-methylphenyl) l-aziridinyl) phosphine oxide tri(2-ethyl-3-(3-n-propylplienyl) l-aziridinyl) phosphine oxide tri(2-hexyl-3-(3-n-propylphenyl) l-aziridinyl) phosphine oxide tri(2-heptyl-3-(2,4dimethylphenyl) l-aziridinyl) phosphine oxide tri(1-aziridinyl) phosphine sulfide tri(Z-methyl-l-aziridinyl) phosphine sulfide tri(2,3-dimethyl-l-aziridinyl) phosphine sulfide tri(2,3-diethyl-l-aziridinyl) phosphine sulfide tri(2-methyl-3-isopropyl-l-aziridinyl) phosphine sulfide tri(2-tert-butyl-l-aziridinyl) phosphine sulfide tri(2,3-didecyl-1-azi1'idinyl) phosphine sulfide tri(2-ethyl-3-pentadecyl-l-aziridinyl) phosphine sulfide tri(2-eicosyl-l-aziridinyl) phosphine sulfide tri(2-methyl-3-cyclohexyl-l-aziridinyl) phosphine sulfide tri(2-phenyl-l-aziridinyl) phosphine sulfide tri(2-phenyl-3-benzyl-l-aziridinyl) phosphine sulfide tri(2,3-diphenyl-l-aziridinyl) phosphine sulfide tri(2-ethyl-3-pheny1-l-aziridinyl) phosphine sulfide tri(2-amyl-3-benzyl-l-aziridinyl) phosphine sulfide Another group of useful compounds are the substituted melamines such as tripropylene and tributylene melamin imines of the structures:

wherein R is a lower alkyl radical having from 1 to 4 carbon atoms and n. varies from 1 to 8. Particularly useful are those compositions where R=methyl or ethyl and 11:8.

An additional useful group of curing agents are the alkylene derivatives of trimesic acid. These compounds are included within the formula:

accelerate the epoxy/carboxyl portion of the cure, particularly at lower (less than C.) temperatures.

As indicated by the specifications listed above, where epoxy compositions are used as curing agents, the epoxy resin can be of diverse structure either aliphatic, aromatic, or heterocyclic. Apparently, the nonepoxide portion of the resin does not play an important part in the curing mechanism. For example, satisfactory results have been obtained when alkyl, alkene, alkylne or various aromatic epoxides have been utilized. The main requirement being that at least two, preferably more than two, reactive epoxide groups are available in the molecule.

Resins falling within this specification are manufactured by many prominent manufacturers and illustrative resins are described in their sales literature. Illustrative examples are ERLA-0510 B04000 and EPON-SOl-X Additional epoxide resins which can be used normally include any commercial epoxide resin falling within this general specification range:

Epoxy equivalence/ grams 0.85 to 1.50 Functionality 2.0 to 4.0 Molecular weight 100 to 800 Stabilizer.-T11e stabilizers of this invention are of diverse structure and are difiicult to catagorize. Many, but not all of these structures have been found to contain sulfur and nitrogen usually bound in a heterocyclic ring and have weakly basic characteristics. Further, many of these have aliphatic or heterocyclic substituents. However, some compositions which do not contain heterocyclically bound nitrogen or sulfur have been found to be good stabilizers. For this reason, no attempt is made to generically describe the stabilizers of this invention. The generic structures are shown below. Table I, which follows, lists the structural formula of a few of the preferred stabilizers. It is known that other similar compounds would function as stabilizers and it is suspected that many others not listed herein would also function as stabilizers.

t 1l ]1PgON801-X has an epoxy equivalence/100 grams of 0.75

TABLE I.-STRUCTURAL FORMULAS FOR COMPOUNDS LISTED AS STABILIZERS No. Trade name Chemical name Chemical structure Vendor 1.4. Flectol H 1,2d1hydro-2-2-A-trimethyl- H Monsanto quinollne (polymerized I CH; Chemical product) N Company.

(polymerized) 2.-T.:.::::: Sullasan R. 4,4 -dithiodimerpholine....: CHz-GH: GHQ-CH2 Do.

O\ NSS-N /O C Hz- 0 H: C Hr- C H:

3 Altax. 2:3: Benzothlazyl disulflde-...... S S RT Vanviygi derbilt. N 1

L-Zzntz: ZC528.....-:::: -Phenylenethionylamiue NSO Thiokol or s,n disulfynyl-p- Chemical phenylenediamine. Corporatlon.

NSO

5....:::-.:;::':. Nona-":2: Phenylthionylsmlne or sul- Do.

finylaniline. N S 0 such as potassium, lithium or ammonium, hydrazinium nitroforrn, nitronium and nitryl perchlorates as well as other high energy oxidizers.

Binders.--The binders of this invention are saturated and unsaturated hydrocarbon polymers. A favored group are the polyalkadienes containing reactive sites such as hydroxy, carboxy, carbonyl, epoxy, amino, imino and the like. Most of these polymers are commercially available products or can be made using known polymerization procedures. For example, polyalkadiene containing carboxyl groups can be prepared by polymerizing or reacting many materials including conjugated dienes containing from 4 to 8 carbon atoms such as 1,3-butadiene, isoprene, piperylene, methylpentadiene, 2-ethyl-1,3-butadiene, phenylbutadiene, 3,4-dimethyl-l-3-hexadiene, 4,5-diethy1-l,3-

octadiene. In addition, conjugated dienes containing reactive substituents along the chain can also be employed, such as for example, halogenated dienes, such as chloroprene, fluoroprene, etc. Of the conjugated dienes, the preferred material is butadiene, with isoprene and piperylene also being especially suitable. In addition to the conju- TABLE I\Conttnued No. Trade name Chemical name Chemical structure Vendor 6 Flexzone 6H.- Nphenyl-N'eyclohexybp- Naugatuek.

phenylene dlamine 7 Thlurad O. 'letramethylthluram disul- CH; CH; Monsant fide Chemical /N(i S S--(fi-N Company. CH; 5 s CH:

S t 26.- 2- 2,6 di th l-4-mo ho- S H; D0, an 0cm iinothi i be wtmazgie. W g, 1/

CHI

9 BenzothiaZole- Benzothiazole S\ c 10 Santoeure NS. N-tert-butyl-2-benzothia- CH Do.

zolesulfenamide. S l

S-NHC-CHi e e l Do. 11 DPG Diphenvlguanid n I 12 DOTG Dlorthotolyl-guanldine I|-IH NH(NH -CH; CH:

TABLE H gated dienes, other monomers which can be employed are aryl-substituted olefins, such as styrene, various alkyl Additional referred stabilizers styrenes, paramethoxystyrene, vinylnaphthalene, vinyl- P tl dthl'k ht l' t" ouene, an e l e; eerocyc 1c mtrogen-con aining $355 3 533,133,135? monomers, such as pyridine and quinoline derivatives (3) henylenediamine containing at least one vinyl or alphamethylvinyl group, (4) u all ig g such as 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, henykphenylfinediamine 3-ethyl-5:vinylpyr idine, 2-methyl5-vinylpyridine, 3,5-diethyl-4-v1nylpyr1d1ne, etc. In addition, monoand disubsti- NN-d1tolyl-p-phenylenediamine and NN, dixylyl p phenylenediamine 50 tuted alkenyl pyridlnes and the like quinolines; acrylic acid esters, such as methyl acrylate, ethyl acrylate, alkacrylic acid esters, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, vinyl ether, vinyl chloride, vinylidene chloride, vinylfuran, vinylcarbazole, vinylacetylene, etc. can be used as polymer substrates.

The above compounds, in addition to being polymerizable alone, are also copolymerizable with each other and may be copolymerized to form terminally reactive polymers. In addition, copolymers can be prepared using minor amounts of copolymerizable monomers containing more than one vinylidene group such as 2,4-divinylpyridine, divinylbenzene, 2,3-divinylpyridine, 3,5-divinylpyridine, 2,4-divinyl-6-methyl-6-methylpyridine, 2,3-divinyl-S- ethylpyridine, and the like.

Another group of superior binders are the saturated binders containing free carboxyl sites. These binders, which are the condensates of saturated glycols and saturated acids, are advantageous in certain respects compared to the corresponding polyalkadiene binders. For example, they are more energetic on a weight by weight basis and they are more compatible with HP However, in the absence of the inventive stabilizers, the curability of these saturated hydrocarbon binders in the presence of HP is no more satisfactory than that of the unsaturated binders. A specific saturated binder which is favored is the condensate of neopentyl glycol and Emery 3389 (a dimer acid condensation polymer sold by Emery Industries). Favored are the halogenated saturated binders such as the carboxyl containing fluoroalkanes.

The polymeric fuel binders of this invention can range in molecular weight from 250-12,000 or more, although the most satisfactory results have been obtained using carboxyl terminated hydrocarbon polymers ranging in molecular weight between 5 -6,000. As indicated, especially favored are the carboxyl terminated polybutadienes and the neopentyl glycol condensate of that molecular weight range.

Propellant adjuvants.In addition to the curing agents, solvents, accelerators, polymerization and vulcanization catalysts and the like which are included within the fuel binder content of the inventive propellant compositions, certain additives, ignition catalysts, conditioning or modifying agents, surfactants, high energy metals, their hydrides and the like can often be advantageously added to the propellant compositions to alter or improve their physical and combustion characteristics. For convenience sake, these substances are herein generically referred to as propellant adjuvants and they can be present in the finished propellant composition in amounts up to about 30 parts by weight down to 0 parts by weight of the final propellant composition.

More commonly, however, the adjuvants comprise from about 20 parts by weight or even less down to about parts by weight of the propellant compositions. Among the many propellant adjuvants which can be used are included the following typical materials: plasticizers such as the alkylphthalates and the like, and darkening agents such as carbon black or lamp black, ballistic agents such as potassium sulfate, hygroscopicity inhibitors such as dinitro-toluene and various coolants, combustion and burning rate catalysts. The combustion catalysts are of diverse structure but generally are compounds containing oxygen. These catalysts can be inorganic or organic compounds. They include, among many others, such as ferrous, ferric, magnesium, titanium, calcium, molybdenum, and vanadium oxides and the like. Especially effective as combustion catalysts are the chromates and dic'hromates, generally with ammonium dichromate being a preferred catalyst. Organics such as nitrocellulose can also be effectively used.

A favored group of adjuvants are the finely divided lightweight and high energy metals and nonmetals such as aluminum, beryllium, boron, silicon and the like. These materials can be used by themselves, as their carbides and hydrides, or they can be employed in the form of their polymer coated particles.

Compounding the propellant mixtures.--In preparing the stabilized solid propellant composition of this invention, the following preferred procedure, among many others, can be used.

The dried, finely divided HP oxidizer including other oxidizers and the combustible fuel binder including ouring agents and catalysts are placed in a blending vessel equipped with an efiicient spark proof mixer and blended to a homogenous mixture. To this mixture is added any optional propellant adjuvants such as the finely divided high energy metals or metalloids. During these additions, eflicient mixing is maintained until a homogenous mixture results. The total mixing time necessary for a uniform mixture varies according to the batch size, but ordinarily, at least 30 minutes of mixing is required with 90 minutes or more representing the exertme time. Finally, the curing agent(s) or catalysts are added and the mixing continued for an additional /2 to 1 hour. Finally, the uniformly blended uncured viscous propellant composition is cast into a mold of the desired configuration and the propellant mix is cured at the required temperature until the desired hardness is obtained. The temperature during the blending operation is usually around 6686 F. although higher temperatures can be used if desired. The

curing temperatures, as indicated previously, are dependent upon the particular resin used as a binder and the batch size, among other things, and thus cannot be stated with precision. However, the ranges of time and temperature given supra are typical for HP based propellant compositions containg the inventive stabilizers.

Preferred propellant compositions.As indicated supra, for various reasons including better stability, physical and propulsion characteristics, cost and avilability, certain of the novel propellants prepared by the novel process of this invention are preferred to others. In this instance, the preferred propellant compositions of this invention are made up of:

(1) From about 0.5-4.0 parts by weight of a stabilizer selected from the group consisting of:

. the polymer of 1,2-dihydro-2,2,4-trimethyl-quinoline,

4,4'-dithiodimorpholine,

. benzothiazyl disulfide,

. sulfonyl aniline,

N,N-disulfonyl-para-phenylenediamine,

. N-phenyl-N'-cyclohexyl-p-phenylenediamine,

. tetramethylthiuram disulfide,

. 2-(2,6-dimethyl-4-morpholinothio)benzothiazole,

benzothiazole,

. N-tert-butyl-2-benzothiazolesulfenamide,

. diphenylguanidine,

. diorthotolyl-guanidine,

. N,N-diphenyl-p-phenylenediamine,

. N,N-ditolyl-p-phenylenediamine,

. N,N'-dixylyl-p-phenylenediamine, and

. equal mixtures of N,N-diphenyl-phenylenediamine, -N,-N-ditolyl-p-phenylenediamine and N,N-dixylyl-p-phenylenediamine.

(2) From about 60-80 parts by weight of oxidizer including 0-20 parts by weight of ammonium perchlorate oxidizer and 60-80 parts by weight of HP (3) From about 15-25 parts by weight of a binder selected from the group consisting of saturated alkane, carboxyl containing binders having a molecular weight range of from about 500 to 6000 and carboxyl containing polybutadiene having a molecular weight range between about 500-6000.

(4) From about 10-20 parts by weight of a propellant adjuvant selected from the group consisting of particulated beryllium and aluminum powders.

To clarify some of the modifications and variations which can be made in the inventive concept, the following embodiments are submitted:

In one embodiment of this invention, the following propellant components are blended in an appropriately sized mixing vessel equipped with an efficient means of blending, cooling and heating in the manner described.

To a stirred 13% by weight portion of commercially available carboxy terminated polybutadiene having a molecular weight range between 500 and 6000, is added 2 parts by Weight of HX-868 (butylene imine of trimesic acid) curing agent, 1 part by weight of phenylthionylamine stabilizer and 16 parts by weight degreased aluminum powder (having a particle size between 3 and 30 microns. After the mixture appears to be uniform, a 68 parts by weight portion of anhydrous propellant grade hydrazinium diperchlorate is blended in. The blending and mixing operation is continued for an additional 30- minutes and is cast into a /2 pound rocket engine casing. The propellant is cured at F. for 96 hours. The cured propellant had good flexibility and a Shore A durometer hardness of 75. The motors fired successfully and provided a burning rate of 1.0 in./second at 1000 p.s.i. with a burning rate slope of 0.50.

In another embodiment of this invention, the experiment above is essentially repeated except that 16 parts by weight portion of beryllium powder (degreased) is substituted for the same portion of aluminum powder 1 1 used above. The curing conditions and physical properties are substantially the same.

In another embodiment using the same procedure described above, the following propellants are compounded and cured:

Component: Parts by weight Carboxyl terminated polybutadiene having a molecular weight range between 500 and 6000 17 Butylene imine of trimesic acid 2 Aluminum powder 16 HP; 64 Tetramethylthiuramdisulfide 1 The homogenous propellant is cured 96 hours at 150 F. to produce a propellant having good flexibility and Shore A hardness.

In another embodiment, the following components are mixed and cured as before:

Component: Parts by weight Carboxyl terminated polybutadiene having a molecular weight range of between 500 and 6000 l4 Tris-I-(Z-methylaziridinyl)phosphine oxide 2 HP 60 NH ClO 18 Benzothiazole 2 The propellant mix is cured for 96 hours at 150 F. to produce a cure having good Shore A hardness and flexibility.

In yet another embodiment, the following components are mixed and cured at 150 F. for 96 hours as described above.

Components: Parts by weight Carboxyl containing saturated hydrocarbon resin having a molecular weight range of 500 to 5000 obtained by condensing neopentyl glycol and dimer acid of the type (Emery 1,1'-ethylenebis(Z-methyl)aziridine 6.0 Aluminum powder 13.0 HP 60.0 NH ClO 10.0 Equal mixtures of N,N' diphenyl-phenylenediamine, N,N' ditolyl-p-phenylenediamine and N, -dixylyl-p-phenylenediamine 1.0

In still a further embodiment, the following components are mixed and cured at 150 F. for 72 hours as described previously. The above experiment indicates that the stabilizer does more than prevent crosslinking of the binder since the above binder, which has no unsaturation, cannot be satisfactorily cured without stabilizer.

In a preferred embodiment, the following propellant components and stabilizer are admixed and cured as described previously.

Components: Parts by weight Carboxyl terminated polybutadiene (molecular weight 3000-6000) 10.00

'Butylene imine derivative of trimesic acid (I-IX-868) Equal mixtures of N,N' diphenyl-phenylenediamine, N,N' ditolyl-p-phenylenediamine Typical ballistic properties Burning rate at 1000 psi. (in/sec.) Burning rate slope Components: Parts by weight Carboxyl terminated polybutadiene (molecular weight 3000-6000) 10.00 Butylene imine derivative of trimesic acid (HX-868) 4.00 The polymer of 1,2-dihydro-2,2,4-trimethylquinoline 2.00 Aluminum 14.00 HP 70.00

Components: Parts by weight Carboxyl terminated polybutadiene (Molecular weight 3000-6000) 10.00 Butylene imine derivative of trimesic acid (HX-868) 4.00 4,4'-dithiodimorpholine 2.00 Aluminum 14.00 HP 70.00

Components: Parts by weight Carboxyl terminated polybutadiene (Molecular weight 3000-6000) 10.00 Butylene imine derivative of trimesic acid (HX-868) 4.00 Benzothiazyl disulfide 2.00 Aluminum 14.00

Components: Parts by weight Carboxyl terminated polybutadiene (Molecular weight 3000-6000) 10.00 Butylene imine derivative of trimesic acid (HX-868) 4.00 N,N-disulfinyl-para-phenylenedia'mine 2.00 Aluminum 14.00

Components: Parts by weight Carboxyl terminated polybutadiene (Molecular weight 3000-6000) 10.00 Butylene imine derivative of trimesic acid (HX-868) 4.00 N-phenyl-N-cyclohexyl-p-phenylenediamine 2.00 Aluminum 14.00 HP 70.00

Components: Parts by weight Carboxyl terminated polybutadiene (Molecular weight 3000-6000) 10.00 Butylene imine derivative of trimesic acid (BX-868) 4.00 2(2,6 dimethyl 4 morpholinothio)benzothiazole 2.00 Aluminum 14.00 HP 70.00

Components: Parts by weight Carboxyl terminated polybutadiene (Molecular weight 3000-6000) 10.00 Butylene imine derivative of trimesic acid (EX-868) 4.00 N-tert-butuyl-2-benzothiazolesulfenamide 2.00 Aluminum 14.00 HP 70.00

13 Components: Parts by weight Carboxyl terminated polybutadiene (Molecular weight 3000-6000) 10.00 Butylene imine derivative of trimesic acid (HX-868) 4.00 Diphenylguanidine 2.00 Aluminum 14.00 HP 70.00

Components: Parts by weight Carboxyl terminated polybutadiene (Molecular weight 3000-6000) 10.00 Butylene imine derivative of trimesic acid (HX-868) 4.00 Diorthotolyl-guanidine 2.00 Aluminum 14.00 HP 70.00

Components: Parts by weight Carboxyl terminated polybutadiene (Molecular weight 3000-6000) 10.00 Butylene imine derivative of trimesic acid (HX-868) 4.00 N,N'-diphenyl-p-phenylenediamine 2.00 Aluminum 14.00

Components: Parts by weight Carboxyl terminated polybutadiene (Molecular Weight 3000-6000) 10.00 Butylene imine derivative of trimesic acid (HX-868) 4.00 N,N-ditolyl-p-phenylenediamine 2.00 Aluminum 14.00 HP 70.00

Components: Parts by weight Carboxyl terminated polybutadiene (Molecular weight 3000-6000) 10.00 Butylene imine derivative of trimesic acid (HX-868) 4.00 N,N-dixylyl-p-phenylenediamine 2.00 Aluminum 14.00 HP 70.00

As indicated by the various embodiments presented supra, numerous changes and modifications can be made without departing from the inventive concept. The metes and bounds of this invention are best shown by the claims which follow.

I claim:

1. A method for preparing a propellant composition and for curing of the composition to a cast solid flexible propellant, said composition and said solid propellant each acquiring improved physical and aging characteristics from the presence of an admixed stabilizer, said composition comprising hydrazinium diperchlorate oxidizer and a binder selected from the group consisting of polymers of a monomer selected from the following monomers, and copolymers of said monomers, said polymer and copolymer each having a molecular weight in the range from about 250 to about 12,000: i

a conjugated diene containing from 4 to 8 carbon atoms and selected from 1,3-butadiene, isoprene, piperylene, methylpentadiene, 2-ethy1-1,3-butadiene, phenylbutadiene, 3,4-dimethyl-1, 3-hexadiene, 4,5-diethyl-1,3-octadiene;

a halogenated diene selected from chloroprene and an aryl-substituted olefin selected from styrene, alkyl styrene, paramethoxystyrene, vinylnaphthalene, and vinyltoluene;

14 a heterocyclic nitrogen-containing monomer selected from 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 3-ethyl-5-vinylpyridine, 2-methyl-5-vinylpyridine, 3,5- diethyl-4-vinylpyridine;

an acrylic acid ester selected from methyl acrylate and ethyl acrylate;

an alkacrylic acid ester selected from methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methaerylate and pentyl methacrylate;

vinyl ether, vinyl chloride, vinylidene chloride, vinylfuran, vinylcarbazole, and vinylacetylene; and 2,4-divinylpyridine, divinylbenzene, 2,3-divinylpyridine,

3,5-divinylpyridine;

and saturated binders containing free carboxyl sites selected from carboxyl containing haloalkanes and condensates of saturated glycols and saturated acids; the method comprising admixing said oxidizer and binder with a stabilizing amount of a stabilizer composition to form said propellant composition, and casting and curing the admixed composition to a flexible solid propellant, said stabilizer being selected from a group of stabilizing compounds consisting of:

(1) the polymer of 1,2-dihydro-2,2,4-trimethylquinoline,

(2) 4,4'-dithiodimorpholine,

(3) benzothiazyl disulfide,

(4) sulfinyl aniline,

(5) N,N'-disulfonyl-para-phenylenediamine,

(6) N-phenyl-N'-cyclohexyl-p-phenylenediarnine,

(7) diphenylguanidine,

(8) diorthotolyl-guanidine,

(9) N,N'-diphenyl-p-phenylenediamine,

(l0) N,N-ditolyl-p-phenylenediamine,

(11) N,N'-dixylyl-p-phenylenediamine, and

(12) equal mixtures of N,N'-diphenyl-phenylenediamine, N,N'-ditolyl-p-phenylenediamine, and N,N'-dixylyl-p-phenylenediamine; and

a solid propellant cast and cured from said composition.

2. The method of claim 1 wherein the polyalkadiene binder is a carboxyl terminated polybutadiene and the propellant adjuvant is aluminum.

3. The method of claim 2 wherein the stabilizer is the polymer of 1,2-dihydro-2,2,4-trimethyl-quinoline.

4. The method of claim 2 wherein the stabilizer is 4,4- dithiodimorpholine.

5. The method of claim 2 wherein the stabilizer is benzothiazyl disulfide.

6. The method of claim 2 wherein the stabilizer is sulfinyl aniline.

7. The method of claim 2 wherein the stabilizer is N,N'-disulfinyl-para-phenylenediamine.

8. The method of claim 2 wherein the stabilizer is N-phenyl-N'-cyclohexyl-p-phenylenediamine.

9. The method of claim 2 wherein the stabilizer is diphenylguanidine.

10. The method of claim 2 wherein the stabilizer is diorthotolyl-guanidine.

11. The method of claim 2 wherein the stabilizer is N,N'-diphenyl-p-phenylenediamine.

12. The method of claim 2 wherein the stabilizer is N,N'-ditolyl-p-phenylenediamine.

13. The method of claim 2 wherein the stabilizer is N,N'-dixylyl-p-phenylenediamine.

14. The method of claim 2 wherein the stabilizer is equal mixtures of N,N'-diphenyl-phenylenediamine, N, N-ditolyl-p-phenylenediamine and N,N'-dixylyl-p-phenylenediamine.

15. The method of claim 1 wherein the binder is a polyalkane.

16. A homogenous propellant composition for preparing a stabilized cast solid propellant, said composition having improved physical and aging characteristics both in the uncured and cured states, said composition comprising an admixture of the following components in the indicated proportions:

(a) from about 45 to 85 parts by weight of hydrazinium diperchlorate,

(b) from about 10 to 40 parts by weight of a binder selected from the group consisting of polymers of a monomer selected from the following monomers, and copolymers of said monomers, said polymer and copolymer each having a molecular weight in the range from about 250 to about 12,000:

a conjugated diene containing from 4 to 8 carbon atoms and selected from 1,3-butadiene, isoprene, piperylene, methylpentadiene, 2-ethyl- 1,3-butadiene, phenylbutadiene, 3,4-dimethyl- 1,3-hexadiene, 4,5-diethyl-1,3-octadiene;

a halogenated diene selected from chloroprene and fluoroprene;

an aryl-substituted olefin selected from styrene,

alkyl styrene, paramethoxystyrene, vinylnaphthalene, and vinyltoluene;

a heterocyclic nitrogen-containing monomer selected from 2-vinylpyridine, 3-vinylpyridine, 4- vinylpyridine, 3-ethyl-5-vinylpyridine, 2-methyl- 5-vinylpyridine, 3,S-diethyl-4-vinylpyridine;

an acrylic acid ester selected from methyl acrylate and ethyl acrylate;

an alkacrylic acid ester selected from methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate and pentyl methacrylate;

vinyl ether, vinyl chloride, vinylidene chloride, vinylfuran, vinylcarbazole, and vinylacetylcne; and

2,4-divinylpyridine, divinylbenzene, 2,3-divinylpyridine, 3,5-divinylpyridine;

and saturated binders containing free carboxyl sites selected from carboxyl containing haloalkanes and condensates of saturated glycols and saturated acids;

(c) from about to 25 parts by weight of propellant adjuvants, and

(d) from about 0.1 to 6.0 parts by weight of a stabilizer selected from the group consisting of:

(1) the polymer of 1,2-dihydro-2,2,4-trimethylquinoline,

(2) 4,4-dithiodimorpholine,

(3) benzothiazyl disulfide,

(4) sulfinyl aniline,

(5) N,N-disulf0nyl-para-phenylenediamine,

(6) N-phenyl-N'-cyclohexyl-p-phenylenediamine,

(7) diphenylguanidine,

(8) diorthotolyl-guanidine (9) N,N-diphenyl-p-phenylenediamine,

(10) N,N'-ditolyl-p-phenylenediamine,

( 1 1 N,N'-dixylyl-p-phenylenediamine, and

(12) equal mixtures of N,N'-diphenyl-phenylenediamine, N,N-ditolyl-pphenylenediamine 'and N,N'-dixylyl-p-phenylenediamine; and

a solid propellant cast and cured from said composition.

17. The homogenous propellant composition of claim 16 wherein the polyalkadiene is a polybutadiene.

18. The homogenous propellant composition of claim 17 wherein the polybutadiene is carboxyl terminated and has a molecular weight range of about 500 to 5000.

19. The composition of claim 18 wherein the stabilizer is the polymer of 1,2-dihydro-2,2,4-trimethylquinoline.

20. The composition of claim 18 wherein the stabilizer is 4,4'-dithiodimorpholine.

21. The composition of claim 18 wherein the stabilizer is benzothiazyl disulfide.

22. The composition of claim 18 wherein the stabilizer is sulfinyl aniline.

23. The composition of claim 18 wherein the stabilizer is N,N'-disulfinyl-para-phenylenediamine.

24. The composition of claim 18 wherein the stabilizer is N-phenyl-N'-cyclohexyl-p-phenylenediamine.

25. The composition of claim 18 wherein the stabilizer is diphenylguanidine.

26. The composition of claim 18 wherein the stabilizer is diorthotolyl-guanidine.

27. The composition of claim 18 wherein the stabilizer is N,N-diphenyl-p-phenylenediamine.

28. The composition of claim 18 wherein the stabilizer is N,N'-ditolyl-p-phenylenediamine.

29. The composition of claim 18 wherein the stabilizer is N,N-dixylyl-p-phenylenediamine.

30. The composition of claim 18 wherein the stabilizer is equal mixtures of N,N-diphenyl-phenylenediamine, N, N'-ditolyl-p-phenylenediamine and N,N'-dixylyl-p-phenylenediamine.

31. A stabilizer for a stabilized, uncured propellant composition and for the curing of the composition to a stabilized cast solid flexible rocket propellant, said stabilizer imparting improved physical and aging characteristics to said composition both in the uncured and cured states, said stabilized, uncured propellant composition comprising stabilizer, hydrazinium diperchlorate oxidizer and a binder selected from the group consisting of polymers of a monomer selected from the following monomers, and copolymers of said monomers, said polymer and copolymer each having a molecular weight in the range from about 250 to about 12,000:

a conjugated diene containing from 4 to 8 carbon atoms and selected from 1,3-butadiene, isoprene, piperylene, methylpentadiene, 2-ethyl-1,3-butadiene, phenylbutadiene, 3,4-dimethyl-1,3-hexadiene, 4,5-diethyl- 1,3-octadiene;

a halogenated diene selected from chloroprene and fluoroprene;

an aryl-substituted olefin selected from styrene, alkyl styrene, paramethoxystyrene, Vinylnaphthalene, and vinyltoluene;

a heterocyclic nitrogen-containing monomer selected from 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, S-ethyl-S-vinylpyridine, 2-methyl-5-vinylpyridine, 3,5-diethyl-4-vinylpyridine;

an acrylic acid ester selected from methyl acrylate and ethyl acrylate;

an alkacrylic acid ester selected from methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate and pentyl methacrylate;

vinyl ether, vinyl chloride, vinylidene chloride, vinylfuran, vinylcarbazole, and vinylacetylene, and

2,4-divinylpyridine, divinylbenzene, 2,3-divinylpyridine,

3,5-divinylpyridine;

and saturated binders containing free carboxyl sites selected from carboxyl containing haloalkanes and condensates of saturated glycols and saturated acids;

said stabilizer consisting essentially of an admixed tabilizing amount of a stabilizer selected from the group of stabilizing compounds and mixtures thereof consisting of:

(1) the polymer of 1,2-dihydro-2,2,4-trimethylquinoline,

(2) 4,4-dithiodimorpholine,

(3) benzothiazyl disulfide,

(4) sulfinyl aniline,

(5) N,N'-disulfonyl-para-phenylenediamine,

(6) N-phenyl-N'-cyclohexyl-p-phenylenediamine,

(7) diphenylguanidine,

(8) diorthotolyl-guanidine,

(9) N,N'-diphenyl-pphenylenediamine,

(10) N,N'-ditolyl-p-phenylenediamine,

(11 N,N-dixylyl-p-phenylenediamine, and

(12) equal mixtures of N,N'-diphenyl-phenylenediamine, N,N'-ditolyl-p-phenylenediamine and N,N'-dixylyl-p-phenylenediamine; and

References Cited UNITED STATES PATENTS 10/1961 Fox et al. 149-36 X 4/1963 Hudson et al. 149-49 9/1964 Abere et al 149-19 1 1 1964 Vriesen.

4/1965 Hsich.

10 BENJAMIN R. PADGETT, Primary Examiner US. Cl. X.R. 

